Swift

12.3    Catching Errors

Throwing errors is all good and fine, but if the client code isn’t catching and handling them properly, then the work is only half done. In this section, we’ll focus on that second half, completing the groundwork for solid apps.

12.3.1    Direct Pattern Matching

As a framework for the error-catching syntax, Listing 12.10 reintroduces an age-validation example. This time, we are validating the age entered by the user to make it a bit more realistic.

enum AgeValidationError: Error {    case negative    case tooYoung(minimum: Int)}func validateAge(_ age: Int) throws {    if age < 0 { throw AgeValidationError.negative }    if age < 18 { throw AgeValidationError.tooYoung(minimum: 18) }}print("Enter your age: ", terminator: "")let userAge ...